Sorry, might be too late for the fightin'
Royals are pretty up in the air - whatever works for you I'd say.
Light
Plenty of Locust IIc and Firefly
Reasonable numbers of Howler, Ice Storm, Incubus, Jenner IIc, Horned Owl
Medium
Plenty of Griffin IIc and Hunchback IIc
Reasonable numbers of Shadow Hawk IIc, Wyvern IIc, Conjurer
Heavy
Plenty of Glass Spider and Rifleman IIc
Reasonable numbers of Guillotines
Assault
Plenty of Warhammer IIc and Marauder IIc
Reasonable numbers of Highlander
EDIT: adding Royals thoughts based on JFSB mechs:
(a couple don't have Royal variants, but if they're numerous enough I added them)
Stinger, Locust, Mongoose, Hussar
Crab, Phoenix Hawk, Wolverine II, Kintaro
Bombardier, Crusader, Warhammer, Archer
Rifleman II, King Crab, Thug, Stalker